Previously, self-contained gas springs have been constructed with an actuating rod connected to a piston sidably received in a cylinder having a chamber which is precharged at a predetermined pressure, such as 2000 PSI, with an inert gas, such as nitrogen. When the rod and piston are forced into the chamber, the gas therein is compressed to a maximum operating pressure which is usually in the range of about 3,000 to 5,000 PSI, depending on the volume of the chamber and the effective area and stroke of the piston. In normal use, the pressure to which a self-contained gas spring is initially charged is not varied or changed. The spring is initially charged, relieved and recharged through a high pressure valve of the type commonly used in aircraft struts and accumulators.
Previously, gas springs have been constructed with the rod being slidably received in a bearing and retaining assembly received in a tube cylinder. This assembly has a front housing slidably received in a rear housing with a rod gasket or seal therebetween. In use, the gasket is compressed axially so that it expands radially inward into firm sealing engagement with the piston rod by the force produced by pressurized gas in the piston chamber acting on the rear housing. However, in use the rod seal wears away and permits longer strokes of the piston. This results in the piston rod striking the associated dies and causing damage thereto, and/or a rod retainer on the piston head striking the rear housing and causing them to mushroom and/or be damaged. Thus, these self-contained gas springs require considerable maintenance and repair. Moreover, when repair is needed, these gas springs are not easily disassembled, since the bearing assembly, piston rod and retainer must all be removed and replaced through one end of the cylinder housing because a cap is permanently fixed to the other end.